It is not easy to make leads for implantable devices that work well when connected with legacy implantable devices, and yet that also offer sophisticated functions such as addressability when used with modern-day implantable devices, and that further offer the flexibility to work with implantable devices not yet devised.
A typical example of an implantable device is a cardiac pacemaker. Other implantable devices include defibrillators, drug delivery systems, neurological stimulators, and bone growth stimulators.
One of the many challenges facing the designer of a lead is the problem that the designer is not permitted to make very many assumptions about the power provided to the lead by the external equipment such as a pacemaker. The power may be of very limited voltage, perhaps as little as one volt. Yet the main circuitry of the chip in each satellite of the lead is likely to require about two volts to carry out its tasks.